Certain thiazolo-[5, 4-d]-thiazole compounds



3,282,951 CERTAIN THIAZOL-[5,4-d]-TAZOLE COMPOUNDS John D. Spivack, Spring Valley, David H. Steinberg,

Bronx, and Martin Dexter, Briarclifi Manor, N.Y., assignors to Geigy Chemical Corporation, Greenhurgh, N .Y., a corporation of Delaware No Drawing. Filed May 9, 1962, Ser. No. 193,601 2 Claims. (Cl. 260306.8)

This invention relates to stabilization of unstable organic material, in particular to stabilization of polypropylene. The invention also concerns novel stabilizers, especially certain thiazolo-[5,4-d]-thiaz0le stabilizers.

Thiazolo [5,4-d] thiazole compounds are known. However, the particular thiazole compounds of the invention are novel and surprisingly effective in stabilizing polypropylene against deterioration, e.g. due to heat, oxidation, etc.

The surprisingly effective stabilizers of the invention are those of the Formula I:

wherein R and R each independently represent an alkylsubstituted hydroxyphenyl radical containing at least one alkyl group in ortho position to the hydroxyl group on the phenyl nucleus, the hydroxy group preferably being para to the carbon atom joining the phenyl nucleus and the thiazole nucleus.

In the preferred embodiment of the invention, polypropylene is effectively stabilized against deterioration due to heat and oxidation by a stabilizer of the formula:

R4 R (II) wherein R and R represent independently hydrogen or lower alkyl, tertiary butyl being especially preferred in the position ortho to the OH on the phenyl nucleus, and

R and R each independently represent an alkyl group having 4 to 18 carbon atoms, especially tertiary butyl.

Examples of alkyl groups useful in the Formulae I and II are: methyl, ethyl, n-propyl, n-amyl, isoamyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptodecyl, octadecyl.

The term lower alkyl means an alkyl group having from 1 to 6 carbon atoms and includes normal and branched chain groups, as well as primary, secondary and tertiary groups.

Up to the present time, the use of the substituted thiazolo-[5,4-d]-thiazoles of the invention in stabilizing polymeric material, e.g. polypropylene, has not been known. It has now surprisingly been found that polymeric material is stabilized, e.g. against thermal and oxidative deterioration, by incorporating therein effective quantities of one of the substituted thiazoles defined according to the present invention herein-above.

Accordingly, it is an object of the invention to provide stable organic material, preferably stable polymeric material, e.g. polypropylene. In this specification it is under- States Patent 0 3,282,951 Patented Nov. 1, 1966 stood that polymeric material includes polyolefins, such as polyethylene, polypropylene, etc. Preferably, the polyolefins are of high molecular weight, e.g. above 1000 into the hundreds of thousands range. The polyethylenes may be of high density, medium density or low density class. The preferred polymeric material for stabilization is polypropylene.

Polymeric materials such as the foregoing, find use as thermoplastic molding or coating agents. Moreover, because of their high dielectric strength and their resistance to water, they are particularly useful as insulators or dielectrics in condensers and other such equipment. It is known that these polyolefins, e.g. polyethylene and polypropylene, are attacked by oxygen, particularly when exposed to the atmosphere and at elevated temperatures. For example, during use or manufacture the desirable properties of the polyolefins may be impaired dueto oxidative deterioration. Such degradation causes loss in dielectric properties, discoloration, embrittlement, gelation, etc.

Not only homopolymeric material, but also copolymers and physical mixtures thereof are stabilized according to the present invention. For example, high impact polystyrene containing copolymers of butadiene and styrene are stabilized according to the invention.

The invention is also useful in stabilizing lubricating oils of various types including aliphatic esters, such as for example dihexyl azelate, di-(Z-ethylhexyl)-azelate, di- (3,5,5 trimethylhexyl)glutarate, di-(3,5,5-tri methylpentyl)-glutarate, di-(2-ethylhexyl)pimelate, di-(Z-ethylhexyl)adipate, diisoamyl adipate, triamyl tricarballylate, pentaaerythritol tetracaproate, dipropylene glycol dipelargonate, 1,5-pentane-diol-di-(Z-ethylhexanoate), etc.

The stabilizers of the invention are also useful in stabilizing of fatty materials including oils of animal and vegetable origin which tend to deteriorate on standing and exposure to atmospheric oxygen. Among the edible fats and oils within the scope of the present invention are: linseed oil, menhaden oil, cod liver oil, castor oil, olive oil, rapeseed oil, coconut oil, palm oil, corn oil, sesame oil, peanut oil, cotton seed oil, butter, fat, lard, beef tallow, etc. Other oils and fats which deteriorate on standing and exposure to oxygen in the air or oxygen at elevated temperatures, are all within the scope of the present invention.

Within the scope of the invention, also, are saturated and unsaturated hydrocarbons which tend to deteriorate on storage, such as for example, gasolines, both natural and synthetic, in particular, saturated and unsaturated gasolines, etc, jet fuel, diesel oil, mineral oil, fuel oil, drying oil, waxes, resins, etc. Such hydrocarbons are protected against gum formation, discoloration and other deterioration with the stabilizers of the present invention.

It is, therefore, an object of the present invention to provide novel substituted thiazolo-[5,4-d]-thiazole compounds which are versatile and effective stabilizers in at least a single class of the foregoing organic materials which are normally subject to deterioration caused by exposure to heat and/or oxygen, etc. Other objects of the invention will in part be obvious and in part be apparent from what follows.

A particularly preferred stabilizer of the invention is 2,2 bis (3,5-di-t-butyl-4-hydroxyphenyl)-thiazolo=[5,4- d]- thiazole which is especially useful in stabilizing polyolefinic material, e.g. polypropylene and polyethylene, as well as other polymeric material, e.g. polystyrene, in

.Weight for the stabilizer in polyethylene are useful.

particular high impact polystyrene. This thiazolo- [5,4-d]-thiazole is also an effective stabilizer for other unstable organic material, e.g. hydrocarbon oil of mineral origin, gasoline, both natural and synthetic, oils of animal origin, oils of vegetable origin, high temperature lubricating oils, e.g. monoesters or diesters of fatty acids, and aldehydes.

The compounds of this invention may be used also to stabilize organic material in combination with other additive agents, such as for example, antioxidants, pourpoint depressants, corrosion and rust inhibitors, dispersing agents, demulsifiers, antifoaming agents, carbon black, accelerators and other chemicals used in rubber compounding, plasticizers, color. stabilizers, heat stabilizers, UV absorbers, dyes and pigments, fillers, etc.

It is understood that the stabilizers of the invention are not necessarily of equivalent potency. The specific stabilizer most useful to a given unstable material will depend upon several factors for its advantages. Availability and cost of raw materials for the manufacture of the stabilizer and effective inhibitory action of the stabilizer, including duration and degree of activity, are among the factors which control the choice of a specific stabilizer for a specific substrate which is normally sub ject to deterioration. Toxicity, color, stability to light and/or heat and solubility are also important factors. For example, a preferred composition according to the invention comprises from about 0.001% to about 5% by Weight of 2,2'-bis-(3,5-di-t-butyl-4-hydroxyphenyl)-thia zlo[5,4-d]-thiazole and polypropylene.

In general, stabilizers of the invention are employed in a concentration of from about 0.001% to about "by weight preferably from about 0.01% to about 1% by weight. The specific concentration used varies with the substrate and the stabilizer, but the following ranges are preferred.

Concentrations of about 0.001% to about 0.1% by In polypropylene from about 0.05% to about 1% by weight of stabilizer is especially useful. For polystyrene, from about 0.1% to about 1% by weight is useful. In mineral oils, concentrations of from about 0.005% to about 1% by weight of stabilizer are used. Gasolines are stabilized with from about 0.01% to about 0.1% by weight of stabilizer, preferably about 0.05% by weight. Fatty material of animal origin, such as lard, is stabilized with from about 0.001% to about 0.1% by weight of stabilizer. Oils of vegetable origin, such as cotton seed oil, are similarly stabilized with from about 0.001% to about 0.1% by weight of thiazole stabilizer.

Hydrocarbon material, such as cycloolcfins, i.e. cyclohexene, is advantageously stabilized with from about 0.001% to about 1% by weight of the stabilizers of the present invention. Similar concentrations of stabilizer are used to stabilize aldehydes, such as for example, about 0.01% by weight in heptaldehyde. High temperature lubricants which are essentially diesters, e.g. diisoamyladipate, are stabilized with from about 0.5% to about 5%, preferably about 2% by weight of a stabilizer accord ing to the invention.

The stabilizer compounds of the present invention are prepared by reaction of an appropriately substituted aromatic aldehyde with dithioxamide to yield the desired substituted thiazolo-[5,4-d]-thiazole compound. Details of the preparations will be apparent from the examples which follow.

The stabilized compositions of the invention are prepared by incorporation of the stabilizer into the material to be stabilized. If the material subject to deterioration l otherwise indicated and the relationship between parts by weight and parts by volume is as that of grams to cubic centimeters. The temperature is in degrees centrigrade.

EXAMPLE I Preparation of 2,2'-bis-(3,5-di-t-butyl-4-hydroxyphenyl)- thiazolo- [5,4-d] -thiazole 4.7 parts of 3,5-di-t-butyl-4-hydroxybenzaldehyde is reacted with 1.2 parts of dithioxamide in a solution of 50 parts by volume of ethylene glycol at 200 for 15 minutes. The product is obtained by adding 300 parts by volume of water to the cooled reaction mixture and filtering off the precipitate which is washed successively with methanol and hexane and recrystallized twice from benzene. The 2,2'-bis-(3,S-di-t-butyl-4-hydroxyphenyl)- thiazolo-[5,4-d]-thiazole thus obtained is a lemon yellow solid melting at 314315.

Analysis.Calcd for C32H42N202S2: C, H, 7.63%; N, 5.09%. Found: C, 69.68%; H, 7.90%; N, 5.14%.

If in the foregoing Example I, 3,5-cli-t-octyl-4- hydroxybenzaldehyde is substituted then 2,2'-bis-(3,5-di-t-octyl-4- hydroxyphenyl) thiazolo- [5,4-d]-thiazole is obtained. Further, if in the foregoing Example I, 3-octadecyl-4-hydroxybenzaldehyde is used then 2,2-bis-(3-octadecyl-4- hydroxyphenyl)-thiazolo-[5,4-d]-thiazole is obtained.

EXAMPLE II Stabilized composition of polypropylene Unstabilized polypropylene powder (Hercules Profax 6501) is thoroughly blended with 0.5% by weight of 2,2'-bis(3,5-di-t-butyl-4-hydroxyphenyl)-thiazolo-[5,4-d]- thiazole (Example I). The blended material is then milled on a two roller mill at 182 for ten minutes, after which time the stabilized polypropylene is sheeted from the mill and allowed to cool.

The milled polypropylene sheet is then cut into small pieces and pressed for seven minutes on a hydraulic press at 218 degrees and 2000 pounds per square inch pressure. The resultant sheet of 2.5 mil thickness is then tested for resistance to accelerated aging in a forced draft oven at 149 degrees. The so-prepared polypropylene sheet is stabilized against deterioration for more than 800 hours, while an unstabilized sheetwithout any of the stabilizers of Example I-fails and deteriorates after less than 3 hours in the oven under the same conditions.

The following compounds are also useful in stabilizing polypropylene:

All

lower alkyl lower alkyl in which each of R and R is alkyl having from 4 to 18 carbon atoms.

2. 2,2'-bis-(3,5-di-t-buty1-4-hydroxyphenyl) thiazolo- [5,4-d]-thjazole.

References Cited by the Examiner UNITED STATES PATENTS Luten et a1 260620 Campbell 260306.8 Astle et a1. 260306.8

Beaver et a1. 26045.8 Thompson 26045.8

6 3,047,503 7/1962 Jafle et a1. 260619 3,058,952 10/1962 Dexheimer et a1. 26045.8

OTHER REFERENCES 5 Burger: Medicinal Chemistry, (New York), (1960), page 40 Johnson et al., J. Am. Chem. Soc., vol. 82, pages 2719-2724 (1960).

ALEX MAZEL, Primary Examiner.

g NICHOLAS S. RIZZO, JOHN D. RANDOLPH, WAL- TER A. MODANCE, A. D. ROLLINS,

Assistant Examiners. 

1. A COMPOUND OF THE FORMULA 2-(3-R6,4-OH,5-(LOWER ALKYL)-PHENYL), 5-(3-R5,4-OH,5-(LOWER ALKYL)-PHENYL)-THIAZOLO(4,5-D) THIAZOLE 